Contrast ratio (CR) is the ratio of luminance between the brightest “white” and the darkest “black” that can be produced on a display. CR is another influence of perceived picture quality. If a picture has high CR, you will consider it to be sharper and crisper than a picture with lower CR. For example, a typical newspaper picture has a CR of about 5 to 7, whereas a high quality magazine picture has a CR that is greater than 15. Therefore, the magazine picture will look better even if the resolution is the same as that of the newspaper picture.
A typical AMLCD exhibits a CR of approximately 300 to 700 when measured in a dark room. The CR on the same unit measured under ambient illumination is drastically lowered due to surface reflection (glare). For example, a standard 200 nit LCD measured in a dark room has a 300 CR, but will have less than a 2.0 CR under intense direct sunlight. This is due to the fact that surface glare increases the luminance by over 200 nits both on the “white” and the “black” that are produced on the display screen. The result is the luminance of the white is slightly over 400 nits, and the luminance of the black is over 200 nits. The CR ratio then becomes less than 2 and the picture quality is drastically reduce and not acceptable.